Particle screening phenomena in an oblique multi-level tumbling reservoir: a numerical study using discrete element simulation |
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Authors: | Hashem?Alkhaldi Email author" target="_blank">Peter?EberhardEmail author |
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Affiliation: | (1) Institute of Engineering and Computational Mechanics, University of Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany |
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Abstract: | Due to their wide usage in industrial and technological processes, granular materials have captured great interest in recent
research. The related studies are often based on numerical simulations and it is challenging to investigate computational
phenomena of granular systems. Particle screening is an essential technology of particle separation in many industrial fields.
This paper presents a numerical model for studying the particle screening process using the discrete element method that considers
the motion of each particle individually. Dynamical quantities like particle positions, velocities and orientations are tracked
at each time step of the simulation. The particular problem of interest is the separation of round shape particles of different
sizes using a rotating tumbling vertical cylinder while the particulate material is continuously fed into its interior. This
rotating cylinder can be designed as a uniform or stepped multi level obliqued vertical vessel and is considered as a big
reservoir for the mixture of particulate material. The finer particles usually fall through the sieve openings while the oversized
particles are rebounded and ejected through outlets located around the machine body. Particle–particle and particle–boundary
collisions will appear under the tumbling motion of the rotating structure. A penalty method, which employs spring-damper
models, will be applied to calculate the normal and frictional forces. As a result of collisions, the particles will dissipate
kinetic energy due to the normal and frictional contact losses. The particle distribution, sifting rate of the separated particles
and the efficiency of the segregation process have been studied. It is recognized that the screening phenomenon is very sensitive
to the machines geometrical parameters, i.e. plate inclinations, shaft eccentricities and aperture sizes in the sieving plates
at different levels of the structure. The rotational speed of the machine and the feeding rate of the particles flow have
also a great influence on the transportation and segregation rates of the particles. In an attempt to better understand the
mechanism of the particle transport between the different layers of the sifting system, different computational studies for
achieving optimal operation have been performed. |
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Keywords: | Discrete element method Particle simulation Sorting process Sorting machine Particle screening |
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